1. Field of the Invention
The present invention relates to digital equipment such as an electronic computer having a service interruption compensation means which compensates input during service interruption.
2. Description of the Prior Art
In general, in digital equipment such as an electronic computer, electric power must be supplied thereto continuously. Consequently, for abnormal state of the power system such as service interruption, various service interruption compensation means, for example, a battery, a flywheel power source apparatus and the like, are provided.
Digital equipment such, as an electronic computer in almost cases uses an external input power source--for example, a commercial power source of single phase AC 100 V or three-phase AC 200 V in Japan--, and in order to supply the external input to various logical circuits of the digital equipment stably there is provided an internal power unit which converts the AC input into DC stabilized output.
In the prior art, as an example of a system where the external input power source is used and DC stabilization is performed by the internal power source unit as above described, a "power supply system" is disclosed in "Handbook for Electronics and Communication Engineers" edited by the Institute of Electronics and Communication Engineers of Japan and published by Ohmsha Ltd., p. 1305-1306.
Referring to a block connection diagram of FIG. 1, the power supply system comprises a power conversion device 10 installed within digital equipment 1 such as an electronic computer. Lead wires of a commercial power source 101 are connected to the power conversion device 10 from outside of the digital equipment 1, and internal wirings to supply stabilized DC output 102 are connected to each part of an internal circuit (not shown) of the digital equipment 1.
Next, operation will be described. A power switch is first turned on, thereby the commercial power source 101, e.g., AC 100 V, 50 Hz, is transformed and converted into DC 12 V in the power conversion device 10 installed within the digital equipment 1, which voltage is supplied to each part of the circuit of the digital equipment 1. Thus the digital equipment 1 acts to perform operation and processing of data for a definite object according to a prescribed program.
Since such digital equipment 1 reads a program stored in a memory and performs. the data processing in sequence, if a service interruption of the commercial power source 101 occurs, normal operation based on the above-mentioned program cannot be performed during the interruption. Consequently, after the service recovery, the data processing may still remain stopped an abnormal operation, for example, runaway state of the circuit, may be produced.
In recent years, as shown in FIG. 2, an uninterruptible power supply system 2 having a rectifier circuit 21, a battery 22 and an inverter circuit 23 is installed outside the digital equipment 1, where DC voltage is supplied from the battery 22 to the inverter circuit 23 during service interruption of the commercial power source 101, and further voltage of DC-AC conversion by the inverter circuit 23 is supplied to the power conversion device 10. According to this constitution, even if a service interruption of the commercial power source occurs, the power supply to the digital equipment 1 can be continued through the inverter 23 so that abnormal or runaway state of the operation due to the service interruption can be effectively prevented.
In this digital equipment 1, however, since the uninterruptible power supply system 2 of large scale to compensate the service interruption must be provided separately from the digital equipment, this constitution becomes uneconomical.
The uninterruptible power supply system 2 is usually provided with a complicated wave shaping circuit to output sinusoidal AC voltage; thereby increase of the cost is inevitable and the efficiency is reduced.
Furthermore, in case that service interruption state continues longer than the compensation time of the battery, the above-mentioned digital equipment cannot perform the normal operation based on the program, and after the service recovery the data processing may still remain stopped or runaway state of the circuit may be produced.